1. Field of the Invention
The present invention relates to perpendicular magnetic recording heads which apply a perpendicular magnetic field to a recording medium, such as a disk with a hard layer, to record data on the medium. In particular, the invention relates to a perpendicular magnetic recording head including a primary magnetic pole having a flat top surface and an integrated shield layer including side shields disposed at the sides of the primary magnetic pole and an upper shield disposed over the primary magnetic pole, and to a method for manufacturing the perpendicular magnetic recording head. The magnetic recording head having such a structure exhibits low noise, and prevents side fringing and erasure of recorded signals.
2. Description of the Related Art
Perpendicular magnetic recording is one of the techniques for high-density recording of magnetic data on a recording medium, such as a disk. Perpendicular magnetic recording has an advantage in high-density recording in comparison with horizontal magnetic recording.
For high-density recording, the intervals between recording tracks are reduced as the track width Tw of the primary magnetic pole is reduced. Accordingly, perpendicular magnetic recording heads adaptable to high-density recording make worse the problems of write fringing in recording media resulting from the spread of magnetic flux generated for writing from the primary magnetic pole and of erasing recorded signals in the adjacent recording tracks.
In view of such circumstances, some perpendicular magnetic recording heads have been developed which are provided with shields absorbing flux (side flux) spread to the sides of the magnetic pole before the flux reaches the recording medium so as to prevent the side flux from writing onto a recording medium and thus suppress write fringing and erasure of recorded signals.
In order to absorb a large amount of side flux in this magnetic head, it is preferable that not only the side shields be provided at both sides of the primary magnetic pole, but also an upper shield be provided over the primary magnetic pole.
The primary magnetic pole is often formed by plating. Unfortunately, the resulting top surface of such a magnetic pole bulges, and it is thus difficult to form a flat surface. A non-flat upper surface of the primary magnetic pole distorts signals to be recorded and thus hinder accurate recording on recording media, consequently causing noise during reproduction of the recorded signals. It is therefore preferable that the top surface of the primary magnetic pole be formed flat.
A perpendicular magnetic recording head having this structure has been disclosed in a non-patent document One Terabit Per Square Inch Perpendicular Recording Conceptual Design, IEEE TRANSACTIONS ON MAGNETICS, Vol. 38, No. 4, July 2002 (particularly in FIG. 4) and a patent document Japanese Unexamined Patent Application Publication No. 2-201710 (particularly in FIG. 16 B).
In order for the side shields and the upper shield to absorb a large amount of side flux, it is necessary to increase the total flux absorption of the shields. Hence, the side shields and the upper shield are formed in a single piece rather than in separated pieces.
The non-patent document proposes a perpendicular magnetic recording head having side shields and an upper shield which are integrated into one piece. However, this document does not teach how the structure is provided.
In order to integrate the side shields with the upper shield, the following process, as shown in FIGS. 26 to 28, is generally applied.
FIGS. 26 to 28 are fragmentary front views showing a process for manufacturing a perpendicular magnetic recording head having side shields and an upper shield formed in a single piece.
First, after forming a plating base layer 102 on a nonmagnetic material layer 101, a magnetic material is deposited to form a primary magnetic pole 103 on the plating base layer 102 by frame plating or the like, as shown in FIG. 26.
Turning to FIG. 27, another nonmagnetic material layer 104 is formed over the primary magnetic pole 103 from the top to the sides, and a gap layer 105 is further provided over the nonmagnetic material layer 104.
Then, a shield layer 106 made of a magnetic material is formed over the gap layer 105 from above the primary magnetic pole 103 to the sides, as shown in FIG. 28. The shield layer 106 is cut to a predetermined height (for example, along line D-D in the figure). Thus, an integrated shield serving as side shields and an upper shield is provided.
However, the top surface of the primary magnetic pole 103 of this magnetic head is undesirably formed in a convex shape in the step shown in FIG. 26. Consequently, the resulting perpendicular magnetic recording head distorts record signals to increase noise.
It is therefore considered that the top surface of the primary magnetic pole 103 of the non-patent document is not flat and is accordingly liable to produce noise.
In order to flatten the top surface of the primary magnetic pole 103, the following process is generally applied.
FIGS. 29 to 34 are fragmentary front views showing a process for manufacturing a perpendicular magnetic recording head whose primary magnetic pole has a flat top surface.
First, after forming a plating base layer 102 on a nonmagnetic material layer 101, a magnetic material is deposited to form a primary magnetic pole 103 on the plating base layer 102 by frame plating or the like, as shown in FIG. 29.
Turning to FIG. 30, another nonmagnetic material layer 104 is formed over the primary magnetic pole 103 from the top surface to the sides. Then, a first shield layer 110 is formed of a magnetic material over the nonmagnetic material layer 104, as shown in FIG. 31. The first shield layer 110 is cut along line D-D, shown in FIG. 31, together with the upper portion of the primary magnetic pole 103 so that a flat top surface 103a of the primary magnetic pole 103 is exposed at the surface of the first shield layer 110, as shown in FIG. 32.
Then, a gap layer 105 is formed over the first shield layer 110 and the upper surface 103a of the primary magnetic pole 103.
Turning to FIG. 34, a second shield layer 111 is formed over the gap layer 105 and is subsequently cut to a predetermined height (for example, along line D-D in the figure). Thus, the flat top surface 103a is provided to the primary magnetic pole 103 of the perpendicular magnetic recording head.
In the resulting perpendicular magnetic recording head shown in FIG. 34, the first shield layer 110 serves as the side shields and the second shield layer 111 serves as the upper shield.
However, since the first shield layer 110 and the second shield layer 111 are separated by the gap layer 105, they will be magnetically saturated in a short time. Thus, the shields cannot absorb a large amount of side flux as a whole, and consequently cannot prevent side fringing or erasure of recorded signals effectively.
The above-mentioned patent document discloses a perpendicular magnetic recording head having side shields disposed at both sides of the primary magnetic pole and an upper shield disposed over the primary magnetic pole in FIG. 16B of the document. The side shields and the upper shields in this structure are also separated. Although the patent document does not clearly describe the process for manufacturing such a perpendicular magnetic recording head, the head is considered to be made through the foregoing steps shown in FIGS. 29 to 34. Thus, the shields of the patent document do not also absorb a large amount of side flux as a whole, and consequently cannot prevent side fringing or erasure of recorded signals effectively
As described above, in a perpendicular magnetic recording head having an integrated shield serving as side shields and an upper shield, the primary magnetic pole inevitably has a convex top surface, and such a non-flat top surface distorts record signals to increase noise. On the other hand, in a perpendicular magnetic recording head whose primary magnetic pole has a flat top surface, the side shields and the upper shield are inevitably separated, and consequently cannot prevent side fringing or erasure of recorded signals effectively.
Hence, to flatten the top surface of the primary magnetic pole and to form the side shield and the upper shield in a single piece have been mutually contradictory.